Tungstophosphoric Acid-Polyacrylamide Composites for its Application as Catalyst in Quinoline Synthesis

D. BENNARDI; G. ROMANELLI; J.C. AUTINO; L. PIZZIO; M. BLANCO

Strasbourg

Conferencia; Second International Conference on Multifunctional, Hybrid and Nanomaterials; 2011

The preparation and characterization of materials based on tungstophosphoric acid (TPA) immobilized in polyacrylamide (PAA) is presented, and their application as catalysts in the synthesis of quinolines, which possess interesting physiological properties, through condensation of 2-aminoacetophenones or 2 aminobenzophenones and b-ketoesters. The catalysts were prepared from a solution of TPA (different amounts) and PAA in formamide-water, which is pourred on HCl. The TPA/PAA spheres formed were washed, dried, and calcined at different temperatures. By FT-IR, the main TPA bands were observed overlapped to the PAA spectrum, though the tungstophosphate anion into the lacunar species decomposition was not detected. The thermal analysis indicated that the samples are thermally stable up to 200 ºC, imidation of the amido groups and nitrile group formation occurs up to 300 ºC, and at higher temperatures the imide decomposition and the polymeric chain rupture takes place. TPA is mainly highly dispersed in the polymeric matrix as a non crystalline phase, as observed by XRD. Very strong acid sites, and a number of acid sites decreasing with TPA amount and calcination temperature, were determined in the catalysts by potentiometric titration with n-butylamine. The influence of different parameters was tested in the reaction: TPA amount in the polymeric matrix, calcination temperature of the catalyst, reaction time. The different quinolines were obtained with high conversion and selectivity. So, new hybrid catalysts were prepared as an excellent option to carry out acid reactions in polar media with environmental advantages compared to classical catalysts.